llvmbot wrote:
@llvm/pr-subscribers-llvm-transforms
@llvm/pr-subscribers-pgo
Author: Paul Kirth (ilovepi)
Changes
Issue #56502 describes an enhancement related to the use of llvm.expect.
The request is for a diagnostic mode that can identify branches that
would benefit from the use of llvm.expect based on the branch_weights
assigned from a PGO or sample profile.
To support identify branches(or switches) that would benefit from the
use of an llvm.expect intrinsic, we follow a similar checking pattern to
that used in MisExpect, but only in cases where MisExpect diagnostics
would not be used (i.e., when an llvm.expect intrinsic has already been
used).
---
Full diff: https://github.com/llvm/llvm-project/pull/96523.diff
8 Files Affected:
- (modified) llvm/include/llvm/IR/LLVMContext.h (+2)
- (modified) llvm/include/llvm/Target/TargetOptions.h (+4)
- (modified) llvm/include/llvm/Transforms/Utils/MisExpect.h (+3)
- (modified) llvm/lib/IR/LLVMContext.cpp (+6)
- (modified) llvm/lib/IR/LLVMContextImpl.h (+4)
- (modified) llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp (+1)
- (modified) llvm/lib/Transforms/Utils/MisExpect.cpp (+137-36)
- (added) llvm/test/Transforms/PGOProfile/missing-annotation.ll (+110)
``diff
diff --git a/llvm/include/llvm/IR/LLVMContext.h
b/llvm/include/llvm/IR/LLVMContext.h
index 89ad6f1572c67..94e526d465c8e 100644
--- a/llvm/include/llvm/IR/LLVMContext.h
+++ b/llvm/include/llvm/IR/LLVMContext.h
@@ -212,6 +212,8 @@ class LLVMContext {
void setMisExpectWarningRequested(bool Requested);
void setDiagnosticsMisExpectTolerance(std::optional Tolerance);
uint32_t getDiagnosticsMisExpectTolerance() const;
+ bool getAnnotationDiagsRequested() const;
+ void setAnnotationDiagsRequested(bool Requested);
/// Return the minimum hotness value a diagnostic would need in order
/// to be included in optimization diagnostics.
diff --git a/llvm/include/llvm/Target/TargetOptions.h
b/llvm/include/llvm/Target/TargetOptions.h
index d3464b5202ff3..447b86f69cfaa 100644
--- a/llvm/include/llvm/Target/TargetOptions.h
+++ b/llvm/include/llvm/Target/TargetOptions.h
@@ -377,6 +377,10 @@ namespace llvm {
/// By default, it is set to false
unsigned MisExpect : 1;
+/// When set to true, enable MissingAnnotations diagnostics
+/// By default, it is set to false
+unsigned MissingAnnotations : 1;
+
/// When set to true, const objects with relocatable address values are put
/// into the RO data section.
unsigned XCOFFReadOnlyPointers : 1;
diff --git a/llvm/include/llvm/Transforms/Utils/MisExpect.h
b/llvm/include/llvm/Transforms/Utils/MisExpect.h
index e9fba47c97a4d..118d859f93dd6 100644
--- a/llvm/include/llvm/Transforms/Utils/MisExpect.h
+++ b/llvm/include/llvm/Transforms/Utils/MisExpect.h
@@ -76,6 +76,9 @@ void checkExpectAnnotations(Instruction ,
const ArrayRef ExistingWeights,
bool IsFrontend);
+void checkMissingAnnotations(Instruction ,
+ const ArrayRef ExistingWeights,
+ bool IsFrontendInstr);
} // namespace misexpect
} // namespace llvm
diff --git a/llvm/lib/IR/LLVMContext.cpp b/llvm/lib/IR/LLVMContext.cpp
index 8120cccace40b..e1a05c1347969 100644
--- a/llvm/lib/IR/LLVMContext.cpp
+++ b/llvm/lib/IR/LLVMContext.cpp
@@ -171,6 +171,12 @@ void LLVMContext::setDiagnosticsMisExpectTolerance(
uint32_t LLVMContext::getDiagnosticsMisExpectTolerance() const {
return pImpl->DiagnosticsMisExpectTolerance.value_or(0);
}
+void LLVMContext::setAnnotationDiagsRequested(bool Requested) {
+ pImpl->AnnotationsDiagsRequested = Requested;
+}
+bool LLVMContext::getAnnotationDiagsRequested() const {
+ return pImpl->AnnotationsDiagsRequested;
+}
bool LLVMContext::isDiagnosticsHotnessThresholdSetFromPSI() const {
return !pImpl->DiagnosticsHotnessThreshold.has_value();
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 5f8df87149f04..59eb5eb29705d 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -1495,6 +1495,10 @@ class LLVMContextImpl {
std::optional DiagnosticsMisExpectTolerance = 0;
bool MisExpectWarningRequested = false;
+ /// Enables Diagnostics for Missing llvm.expect annotations on extremely hot
+ /// branches
+ bool AnnotationsDiagsRequested = false;
+
/// The specialized remark streamer used by LLVM's OptimizationRemarkEmitter.
std::unique_ptr LLVMRS;
diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 572d37a2b3e55..0fbf60194696a 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -2261,6 +2261,7 @@ void llvm::setProfMetadata(Module *M, Instruction *TI,
} dbgs() << "\n";);
misexpect::checkExpectAnnotations(*TI, Weights, /*IsFrontend=*/false);
+
